Combination fluid coking and calcining



Nov. 24, 1964 c. w. TYSON COMBINATION FLUID coxzuc AND CALCINING FiledJan. 3. 1961 Inventor Charles W. Tyson By w Patent Attorney UnitedStates Patent 3,158,566 COMBENATIQN FLUID CURING AND CALCINDIG CharlesW. Tyson, Summit, NJ., assignor to Essa Research and EngineeringCompany, a corporation of Delaware Filed Jan. 3, 1961, Ser. No. 80,19610 tClaims. (Cl. 208-427) This invention relates to a novel integratedcoke calcining process. More particularly, it relates to an integratedcoke calcining process wherein the coke is heated at a high velocity fora short contact time in the form of one or more confined streams priorto the calcining operation.

In the coking of heavy hydrocarbon oils such as heavy crudes,atmospheric and vacuum still crude residua, tars, pitches, etc., eitherfor the production of fuel products, such as gasoline and gas oils, orfor the production of chemical raw materials, such as aromatics andolefins, one of the major lay-products is petroleum coke. Typically,such feeds can have an initial boiling point of about 700 F. or higher,an A.P.I. gravity of about 0 to 20, e.g., 1.9, and a Conradson carboncontent of about 5 to 40 wt. percent, e.g., 30 wt. percent. The amountof coke formed depends on the character of the materials being processedand, to some extent, upon the coking conditions. In the case of highConradson carbon stock, such as residuum from Hawkins crude, the cokeyield can be 20 wt. percent or higher on the residuum. Gther stocks havebeen found wherein the yield can be as high as 35 wt. percent. Thecoking of other hydrocarbon feeds, both liquid and gaseous, may beaccomplished in a similar manner.

Since the value of the coke as fuel alone detracts from a cokingprocess, more attractive uses for the coke have been sought. One of themajor uses to which the coke has been put has been the manufacture ofelectrodes. Carbon electrodes find their major use in the electricalrefining of alumina to produce aluminum metal. For this purpose,petroleum coke, because of its low ash content, is preferred tometallurgical coke.

Green (uncalcined) petroleum coke contains volatile matter which must beremoved before the material is suitable for electrode purposes. This.removal is accomplished by calcining the coke at a high temperature.This is done commercially at temperatures of 1800 F. to 2400 F. inrotary kilns, vertical retorts, ovens, and the like. The calciningoperation reduces the volatile content of coke to 0.5% or lower of thefinal product, raises its true density, and reduces the electricalresistivity of the known as the fluid coking process. The fluid cokingunit 7 consists basically of a reaction vessel or coker and 'a burnervessel. In a typical operation, the heavy oil to be processed isinjected into the reaction vessel containing a fluidized bed of inertsolid particles, preferably coke particles, maintained at a temperaturein the range of 850 F. to 1200 F., and preferably at 900 F. to 1100 F.,for the production of fuels, or at a higher temperature, e.g., 1200 F.to l600 F., for the production of chemicals, i.e., aromatics andolefins. Uniform temperature exists in the fluidized coking bed. Uniformmixing in the fluidized bed results in virtually isothermic conditionsand eifects almost instantaneous decomposition of the feed stock. In thereaction vessel or coker, the feed stock is partially vaporized andpartially cracked. Product vapors are removed from the coking zone andsent to a frictionator for the recovery of gas and light distillatestherefrom. Any heavy bottoms is usually returned to the coking zone. Thecoke produced in the process remains in the bed coated on the solidparticles thereof.

The heat for carrying out the endothermic coking reaction is generatedin the burner vessel. A stream of coke or coke-coated, solid inertparticles, if the latter are used, is transferred from the reactionvessel or coker to the burner vessel employing a standpipe and risersystem; air being supplied to the riser for conveying the'solids to theburner. Heated coke is then returned to the reaction vessel, usually bymeans'for a standpipe and control valve, thereby completing the cycle.

Sufficient coke or carbonaceous matter is usually burned with anoxygen-containing gas in the burning ves sel to bring the solids thereinup to a temperature sufficient to maintain the system in heat balance.The burner solids are maintained at a higher temperature than the solidsin the reaction vessel. About 5% of coke on the feed is burned for thispurpose. This amounts to approximately 15% to 30% of the coke made inthe process. The unburned portion of the coke represents the net cokeformed in the process. This coke is preferably, withdrawn from theburner, normally cooled and sent to storage. The coke normally containsabout 86% to 94% carbon, 1.5% to 2% hydrogen, 0.5% to 7.5% sulfur, 0.6%to 1.5% volatile matter at 1100 R, up to 6% volatile matter at 950 (3.,and approximately 0.1% to 1.0% ash.

A more complete description of this technique of fluid solids coking canbe obtained by reference to Pfeiifer et al., Patent No. 2,881,130,granted April 7, 1959. The method of fluid solids circulation describedabove is well known in the prior art. This solids handling technique isdescribed in greaterdetail in Packie Patent 2,589,124, issued March 11,1952.

This invention provides an improved method for producing and forcalcining of the coke in a fluidized coke process. The method in oneform comprises treating a stream of hot coke particles from the cokingprocess without substantial cooling for short periods of time and athigh velocities while in the form of a confined elongated stream, i.e.,a conduit, by burning a stream of combustible gases andoxygen-containing gases under conditions so as to minimize the reductionof carbon dioxide to carbon monoxide, and likewise, the reduction ofwater vapor to hydrogen and carbon monoxide. The thusheated coke is thenseparated from the accompanying gases and sent, without substantialcooling, to a moving bed calcining and desulfurizing operation whereinit is subjected to high temperature soaking in order to remove volatilematerial therefrom, to increase its true density, and to lower itselectrical resistivity. The hot combustion gases are separated from theheated cokeparticles at the end of said conduit and then passed throughthe usual heater vessel on the coking unit where they serve to heat thestream of circulating coke particles sufficiently to carry out thecoking operation when recycled to the reaction vessel or coking zone.This method provides In the drawing, 1 is a coking vessel constructed ofsuitable materials for operation at about 9001600 F. A bed of cokeparticles preheated externally of the coking vessel to a sufiicienttemperature to effect the desired coking is made up of suitableparticles in the range of about 70 to 600 microns. For example, the cokeparticles may be preheated to about 1200 F. to maintain an average bedtemperature of about 1000 F. in the coking vessel. The bed of solidparticles reaches an upper level indicated by the numeral 5. The bed isfluidized by means of a gas such as steam entering the vessel at thebottom thereof via pipe 3. The fluidizing gas passes upwardly throughthe vessel at a superficial velocity of about 2 ft. per secondestablishing the solids as a fluidized, liquidsimulating bed having theindicated level. The fluidizing gas serves also to strip vapors andgases from the coke which flows down into the vessel via pipe 9, as willbe later described.

Oil to be converted is preferably preheated to a temperature not aboveits cracking temperature, e.g., 600 F. It is introduced into the bed ofhot coke particles via line 2, preferably at a plurality of points inthe system. The oil upon contacting the hot particles undergoesdecomposition and the vapors resulting therefrom assist in thefluidizing of the solids in the bed and add to its general mobility andturbulent state. The product vapors pass upwardly through the bed andare removed from the coking vessel via line 4 after passing throughcyclone 6 from which solids are returned to the bed via dipleg 7. Astream of solid particles is removed from the coking vessel via line orJ-bend 8 and transported With the assistance of steam and/ or air orother free oxygen-containing gas from lines 9 through riser line 10 intoheating vessel 11. In the heating vessel 11 the solid or coke particlesare maintained as a dense fluidized bed 12 having a level 13 while theyare heated as described hereinbelow to a temperature sufiicient tosupply the heat required to carry out the endothermic reaction occurringin the coking vessel 1. The temperature of the solids in the heatingvessel is usually 100 F. to 300 F. higher than that of the solids in thecoking vessel, e.g., 1200 F. in this example. The bed of coke is in adense turbulent fluidized condition in heating vessel 11 in much thesame manner as the bed in coking vessel 1. The solids are fluidized bythe incoming air and combustion gases as described below. Combustiongases leave the bed of hot particles, pass through one or more cyclones14 and are vented via line 16. Any entrained solids are returned to thebed via dipleg 15. A portion of the hot solids is continually removedfrom heating vessel 11 via valved line 9' and introduced into vessel 1at one or more points in order to maintain heat balance in the reactionor coking portion of the system.

The net make coke, in whole or in part, is removed from the heatingvessel 11 via line 17 without substantial cooling and introduced into atransfer line preheater conduit 18. This transfer, line 18 is heated bythe hot combustion products formed by the supply of air through inletline 19 and fuel gas such as methane, natural gas, refinery make gas, orthe like, through inlet line 20 to burner 21 in vessel 22. Temperaturesin the gas burner or vessel 22 may be about 3000 F. to 3500 F. The hotcombustion products containing about 040% of excess air, or evencontaining less than theoretical air, are discharged from the bottom ofvessel 22 into preheater conduit 18 where they pass cocurrently with thecoke particles heating the same to temperatures of about 2500 F. Coke istransported through the transfer line preheater 18 at high velocities,e.g., -60 ft. per second, so that the contact time is about 1-10seconds. The transported preheated coke and the combustion gases areseparated at the end of the transfer line preheater. The combustiongases are discharged through line 23 into the bottom of heating vessel11 and thence through distribution grid 24 into the dense bed of cokeparticles 12 in order to heat the same by. transfer of the sensible heatin the gases. Additional heat may be provided in vessel 11 by thecombustion of a small portion of the carbonaceous material by the small,residual amount of oxygen in the combustion gases. Additionaloxygen-containing gas may be added to line 23 from line 23A. Thetemperature in the zone in vessel 11 below grid 24 may be lowered byallowing some of the coke above the grid in vessel 24 to flow into thezone below the grid. Or, as an alternate, circulating coke in line 10may enter vessel 11 via line 23.

The preheated coke is discharged from the end of conduit 18 through line25 into the calcining and dcsulfurizing vessel 26.

Calcining and desulfurizing vessel 26 is operated usually with a moving,nonturbulent bed of coke particles maintained at a temperature of fromabout 1800 F. to 2800" F. For some operations, when residence time isless important, a fluidized bed may be used in vessel 26. The cokeparticles are retained in the calcining vessel or soaker 26 for about 3minutes, or up to 5 hours, or as long as necessary to reduce thevolatile content at 950 C. to 0.3% weight or less and to increase thereal density to the maximum obtainable, or reduce the sulfur content tothe desired level. Temperatures in the upper portion of the above range,e.g., 2200 F. to 2800 F., are used when it is desired to produce a lowsulfur coke product and in this case, adequate residence time must beallowed to achieve the desired desulfurization. The calcining vesse orsoaker can be operated batchwise, using more than one vessel if desired.The product coke withdrawn from the soaker through line 27 can be cooledby indirect heat exchange in a waste heat boiler or it can be cooled bywater quenching, or by any other suitable means.

The control of the system will be essentially as follows; however, theremay be other methods to accomplish this end. The level in coking vessel1 will be maintained by the rate of removal of solids from this vesselby actuating valve 28 or other suitable means. The temperature in vessel1 will be controlled by the rate of addition of hot coke by valve andtemperature sensing instrument 29. The level in heating vessel 11 willbe controlled by'the rate of solids removal from thecalciner-desulfurizer by level sensing instrument 30 and valve 31. Thetemperature in heating vessel 11 will be controlled by the temperaturesensing instrument 32, actuating the air and gas supply to burner vessel22. The auxiliary air added to line 23 will also provide a control tothe temperature in vessel 11. The instrument 32 will also control theratio of gas to air to insure the desired degree of combustion of thegas entering line 18. Additional control of temperature, as mentionedabove, may be obtained by the air or oxygen-containing gas admitted fromconduit 23A. The temperature in the calciner-desulfurizer 26 will becontrolled by the rate of coke flow in line 17 as controlled by valve33. Opening valve 33 will lower the temperature in line 18. Solids whichflow in line 18 will fill conduit 25 leading into vessel 26 and anyexcess will flow through line 23 to the heating vessel 11. An alternatemethod for control of the temperature in vessel 26 would be to supplytwo or more inlets and control valves (not shown) from line 17 to line18 at spaced intervals along line 18. By control of the flow among thesespaced inlets, the temperature in vessel 26 may be controlled. Thismethod of control depends on lengthening the exposure time of the solidsto the hot combustion gases for heating to increase solids temperatureand lowering the time of exposureto decrease solids temperature.

Under certain circumstances it is possible to simplify thecoking-calcining process just described. In the more simplified form,soaker vessel 26 would be eliminated and the flow from line 18 wouldproceed through line 23 to vessel 11. In this modification the flow ofcoke through the transfer line 18, wherein calcination takes place,would be large in magnitude compared with the coke production. Hence,essentially all the coke in vessel 11 would have been calcined at leastonce and part of the coke would have been calcined many times. Sincethere are no disadvantages to multiple calcination and only a very minorfraction of the coke would not. have been calcined, the simplificationmentioned ofiers great advantage. In this modification calcined cokewould be withdrawn from vessel 11. The calcined coke so removed may becooled as hereinbefore described.

In order to express this invention more fully, the following co-nditionsor" operation of the various components are set forth as follows:

Conditions in Fluid Coker 1 Broad Preferred Range Range Temperature, F850-1, 600 900-1,100 Pressure, p,s.i.g 1 -50 -15 Superficial Velocity ofD ftJsee 0.2-5 0. 5-3

Conditions in H cater 11 Broad Preferred Range Range Su erficial Velocitof Fluidizing Gas iii sec 0. 2-5 0. 5-3 Temperatyre, F 1, 000-1, 800 1,050-1, 300

Conditions in Transfer Line Preheater 18 Broad Preferred Range RangeTemperature (gas), F 1, 600-4, 000 1, 800-3, 000 Pressure, p.s.i.g 0-50o-40 Superficial Velocity of Fluidizmg Gas,

1't./sec -200 20-100 Contact Time (solids), sec 0.1-100 1-20 Conditionsin Calciner 26 Broad Preferred Range Range Residence Time, hrs 0. 01-10.0 0.1-4.- 0 Temperature, l" 1-. 1, 600-3, 000 1, 700-2, 800 GasVelocity, it./sec 0-10 0.1-1.0 Pressure, p .s.i.g 0-50 3. 0-40. 0

electrodes or in graphite manufacture.

The advantages of this process stem from the fact that a higher yield ofcoke may be obtained at the expense of gaseous fuel due to the fact thatthe heat for the process is obtained by burning an extraneous gaseousfuel and.

not the product coke. In many situations the value of coke isconsiderably higher than that of natural gas or a refinery gas as a fuelsource. The second advantage is that it makes it possible to combine ina single operation, in a simple, efiicient manner, the stepsof cokingand calcining in a single, integrated system or unit.

It is to be understood that this invention is not limited d What isclaimed is:

comprises the steps of coking hydrocarbons by contacting the same withhot coke particles in a coking zone wherein the hydrocarbons areconverted to product vapors and carbonaceous solids are deposited on thecoke particles, removing product vapors from the coking zone,continuously removing a portion of the coke particles from the cokingzone and transferring them to a main heating zone, passing hotcombustion gases through said main heating zone in order to increase thetemperature of said coke particles, returning a portion of the heatedcoke particles from the main heating zone to the coking zone, passing aconfined stream of coke particles without substantial cooling from saidmain heating zone through a transfer line heating zone, passing hotcombustion gases obtained from the burning in a separate burning zone ofan extraneous fuel in the absence of coke particles concurrently withsaid stream of coke particles through said transfer line heating zone inorder to heat the coke particles to calcining temperature, separating atleast a portion of the thus heated coke from the said combustion gases,supplying said combustion gases from said transfer line heating zone tothe bottom of said main heating zone for passage therethrough andheating of the coke particles therein as specified above, passing thehot coke from said transfer line heating zone to a calcining zone,maintaining the coke particles in the calcining zone at a temperature inthe range of 1600 F. to 3000 F. for from about 1 minute to 10 hours andremoving calcined coke from the calcining zone.

2. An integrated coking and calcining process Which comprises the stepsof coking a heavy hydrocarbon oil by contacting the same with a dense,fluidized bed of coke particles at a temperature of about 850 F. to1600" F. in a coking zone wherein the oil is converted to product vaporsand carbonaceous solids are deposited on the coke particles, removingproduct vapors from the coking zone, continuously removing a portion ofthe coke particles from the dense, fluidized bed in the coking zone andtransferring them to a main heating zone, passing hot combustion gasesthrough a bed of said coke particles in said main heating zone toincrease the temperature of said coke particles to about 1000 F. to 1800F., returning a portion of the heated coke particles from the mainheating zone to the coking zone, passing a confined stream of heatedcoke particles from said main heating zone through a transfer lineheating zone, passing combustion gases obtained from the burning in aseparate burning zone of an extraneous fuel at temperatures of from 1600F. to 4000" F. concurrently with said stream of coke particles throughsaid transfer line heating zone to heat the coke particles to calciningtemfor passage therethrough and heating said 'bed of cOke' therein asspecified above, passing the so-heated coke particles separated fromsaid hot combustion gases at the end of said transfer line heater into acalcining zone, maintaining the coke particles in the calcining zone ata temperature in the range of 1600 F. to 3000" F. for

to the specific examples which have been offered merely asillustrations, and that modification may be made without departing fromthe spirit of the invention.

to product vapors and carbonaceous solids are deposited on the cokeparticles, removing product vapors from the coking zone, continuouslyremoving a portion of the 1 coke particles from the dense, fluidized bedin the coking zone and transferring them to a main heating zone, passinghot combustion gases through a bed of said coke particles in said mainheating zone to increase the temperature of said coke particles to about1000 F. to 1800 F, returning a portion of the heated coke particles fromthe main heating zone to the coking zone, passing a confined stream ofheated coke particles from said main heating zone through a transferline heating zone, burning extraneous fuel in a burning zone and passingthe resulting hot combustion gases at a temperature between about 1600F. and 4000 F. concurrently with said stream of coke particles throughsaid transfer line heating zone to heat the coke particles to atemperature between about 1600" F. and 3000 R, separating at least aportion of the thus heated coke from said combustion gases at the end ofthe transfer line heater and supplying said separated combustion gasesto the bottom of said main heating zone for passage therethrough andheating said bed of coke particles therein as specified above, passingthe so-heated coke particles separated from said hot combustion gases atthe end of said transfer line heater into a calcining zone, maintainingthe coke particles in the calcining zone at a temperature in the rangeof 1600 F. to 3000 F. for from about 1 minute to hours and removingcalcined coke from said calcining zone. I

4. The process as defined in claim 1 in which oxygencontaining gas isadded to the combustion gases supplied to the bottom of the main heatingzone to effect the combustion of a small portion of the carbonaceousmaterial therein. 1

5. The process as defined in claim 2 in which oxygencontaining gas isadded to the combustion gases supplied to the bottom of the main heatingzone to eifect the combustion of a small portion of the carbonaceousmaterial therein.

6. The process as defined in claim 3 in which oxygencontaining gas isadded to the combustion gases supplied to the bottom of the main heatingzone to etfect the combustion of a small portion of the carbonaceousmaterial therein.

7. The process as defined in claim 1 in which the superficial velocityof the hot combustion gases in the transfer line heating zone is withinthe range of from 10 to 200 ft./sec. and the contact time of the cokesolids with the combustion gases is in the range of from about 0.1 to100 seconds.

8. The process as defined in claim 2 in which the superficial velocityof the hot combustion gases in the transfer line heating zone is Withinthe range of from 10 to 200 ft./=sec. and the contact time of the cokesolids with the combustion gases is in the range of from about 0.1 toseconds.

9. The process as defined in claim 3 in which the superficial velocityof the hot combustion gases in the transfer line heating zone is Withinthe range of from 10 to 200 ft./ sec. and the contact time of the cokesolids with the combustion gases is in the range of from about 0.1 to100 seconds.

10. An integrated coking and calcining process which comprises the stepsof coking hydrocarbons by contacting the same with hot coke particles ina coking zone wherein the hydrocarbons are converted to product vaporsand carbonaceous solids are deposited on the coke particles, removingproduct vapors from the coking zone, continuously removing a portion ofthe coke particles from the coking zone and transferring them to a mainheating zone, passing hot combustion gases through said main heatingzone in order to increase the temperature of said coke particles,returning a portion of the heated coke particles from the main heatingzone to the coking zone, passing a confined stream of heated cokeparticles from said main heating zone into a transfer line heating zone,burning fluid fuel in a burner zone in the absence of coke particles toprovide hot combustion gases, passing said last mentioned hot combustiongases into said transfor line heating zone for admixture with saidintroduced coke particles, passing the resulting admixture through saidtransfer line heating zone in order to heat the coke particles tocalcining temperature, separating the thus heated coke from the saidcombustion gases, supplying said separated combustion gases from saidtransfer line heating zone to the bottom of said main heating zone forpassage therethrough and for heating the coke particles therein asspecified above, passing the so-heated separated coke particles fromsaid transfer line heating zone to a calcining zone, maintaining thecoke particles in the calcining zone at a temperature in the range of1600 F. to 3000 F. for from about 1 minute to 10 hours and removingcalcined coke from the calcining zone.

References Cited in the file of this patent UNiTED STATES PATENTS

1. AN INTEGRATED COKING AND CALCINING PROCESS WHICH COMPRISES THE STEPSOF COKING HYDROCARBONS BY CONTACTING THE SAME WITH HOT COKE PARTICLES INA COKING ZONE WHEREIN THE HYDROCARBON ARE CONVERTED TO PRODUCT VAPORSAND CARBONACEOUS SOLIDS ARE DEPOSITED ON THE COKE PARTICLES, REMOVINGPRODUCT VAPORS FROM THE COKING ZONE, CONTINUOUSLY REMOVING A PORTION OFTHE COKE PARTICLES FROM THE COKING ZONE AND TRANSFERRING THEM TO A MAINHEATING ZONE, PASSING HOT COMBUSTION GASES THROUGH SAID MAIN HEATINGZONE IN ORDER TO INCREASE THE TEMPERATURE OF SAID COKE PARTICLES,RETURNING A PORTION OF THE HEATED COKE PARTICLES FROM THE MAIN HEATINGZONE TO THE COKING ZONE, PASSING A CONFINED STREAM OF COKE PARTICLESWITHOUT SUBSTANTIAL COOLING FROM SAID MAIN HEATING ZONE THROUGH ATRANSFER LINE HEATING ZONE, PASSING HOT COMBUSTION GASES OBTAINED FROMTHE BURNING IN A SEPARATE BURNING ZONE OF AN EXTRANEOUS FUEL IN THEABSENCE OF COKE PARTICLES CONCURRENTLY WITH SAID STREAM OF COKEPARTICLES THROUGH SAID TRANSFER LINE HEATING ZONE IN ORDER TO HEAT THECOKE PARTICLES TO CALCINING TEMPERATURE, SEPARATING AT LEAST A PORTIONOF THE THUS HEATED COKE FROM THE SAID COMBUSTION GASES, SUPPLYING SAIDCOMBUSTION GASES FROM